Mechanisms of Translation Initiation Mediated by mRNA Structure The Central Dogma of molecular biology is that DNA is used to make mRNA, which is used to make proteins. The initiation of translation, the act of making proteins from messenger RNA (mRNA), is central to the regulation of this process. Dysregulation of translation initiation plays an important role in a number of human diseases including cancer. In eukaryotes including humans, the initiation of translation involves the recruitment of factors that interact with the two (5' and 3') ends of the mRNA to make, in essence, a circle that is poised to be translated. The recruitment of factors and the function of subsequent circularization are poorly understood. We aim to take a novel look at this biological problem through the lens of physical chemistry of nucleic acids and structural biology. Although factor-mediated circularization of mRNA is thought to be critical for protein synthesis, this proposal puts forward an alternative hypothesis: formation of basepairing interactions within the mRNA itself results in the circularization of the mRNA in the absence of the protein complexes. Hence, the ends of the mRNA are inherently located close to one another. Such ?circularization? could facilitate the recruitment of the protein complexes and thereby aid translation initiation. To test our hypothesis, we will experimentally examine whether the ends of mRNAs are in close proximity in the absence of protein initiation complexes. We will also test whether the disruption of basepairing interactions between mRNA ends inhibits protein synthesis and binding of translation initiation factors to the mRNA. The proposed studies will span a spectrum of approaches including single-molecule fluorescent microscopy and fluorescent spectroscopy, chemical probing of RNA structure, computational biology and examination of translation in vivo. Our proposed studies will elucidate whether mRNA secondary structure and end-to-end distance are major determinants that govern translational initiation in eukaryotes.